1. Field of the Invention
The invention relates to destruction of the bonding between a catalyst coating material and its underlying metal support structure, and subsequent removal of the catalyst material from spent, defective, or unused metal support catalytic converters.
2. Brief Description of the Related Art
Acid leach chemistry or purely mechanical means, such as water pressure spraying, are generally utilized to remove certain materials containing catalytic metals from other materials to which they are bonded. For example, catalyst coating material may generally be provided on a supporting structure which is comprised of steel, including steel alloys. The catalyst coating material may be bonded to the supporting structure. Since the catalyst material often comprises valuable metals, such as, for example, platinum, palladium, rhodium or other valuable metals, it is desirable to try to recover these metals. In addition, the catalyst material may also comprise potentially hazardous or toxic metals whose disposal may be highly regulated by various governments. A disadvantage with acid leach processes, which are currently employed to remove the metal catalyst from catalytic converters, is that a significant amount of iron may be leached from the metal support structure. The presence of iron severely complicates the refining of the recovered catalyst metals and may have an adverse effect on the amount of refined platinum, palladium and rhodium that can be ultimately recovered. The prior processes also often employ chemicals which are expensive and may be toxic, and could be likely to harm the environment. Another disadvantage with prior processes is that they tend to leave behind a significant amount of the valuable or hazardous metals. This means that further processing by other means is generally required to effectuate their removal or disposal.
A need exists for an improved process for removing metal containing coatings from a supporting metal structure, and in particular where the coating contains a precious metal and other metals such as nickel, and where the supporting metal structure comprises a steel structure.